db-data-to-csv/src/main/java/com/vcarecity/cvs/service/impl/AbstractSQLQueryService.java

package com.vcarecity.cvs.service.impl;

import com.vcarecity.cvs.core.AutoMapper;
import com.vcarecity.cvs.service.SQLQueryService;
import com.zaxxer.hikari.HikariDataSource;
import lombok.extern.slf4j.Slf4j;

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 * @author Kerry on 19/11/27
 */

@Slf4j
public abstract class AbstractSQLQueryService implements SQLQueryService {

    protected final HikariDataSource dataSource;

    protected AbstractSQLQueryService(HikariDataSource dataSource) {
        this.dataSource = dataSource;
    }

    @Override
    public <T> List<T> queryByPage(String table, int page, int pageCount, Class<T> clazz) throws SQLException {

        final String querySql = getQuerySql(table);

        long startTime = System.currentTimeMillis();


        final Connection connection = dataSource.getConnection();

        final PreparedStatement preparedStatement = getPreparedStatement(connection, querySql, page, pageCount);

        ResultSet resultSet = preparedStatement.executeQuery();

        List<T> list = resultMapper(resultSet, clazz);

        logger.debug("query success. size = {}. usageTime = {} /ms", list.size(), (System.currentTimeMillis() - startTime));

        resultSet.close();
        preparedStatement.close();
        connection.close();

        return list;
    }

    /**
     * 组装表
     *
     * @param table
     * @return
     */
    protected abstract String getQuerySql(String table);

    /**
     * get PreparedStatement
     *
     * @param connection
     * @param sql
     * @param start
     * @param pageCount
     * @return
     * @throws SQLException
     */
    protected abstract PreparedStatement getPreparedStatement(Connection connection, String sql, int start, int pageCount) throws SQLException;

    public <T> List<T> resultMapper(ResultSet resultSet, Class<T> clazz) throws SQLException {
        if (clazz == Object.class) {
            //noinspection unchecked
            return (List<T>) resultSetToObject(resultSet);
        }
        return autoMapper(resultSet, clazz);
    }

    public List<Object[]> resultSetToObject(ResultSet resultSet) throws SQLException {
        final ResultSetMetaData metaData = resultSet.getMetaData();
        final int columnCount = metaData.getColumnCount() - 1;


        int skipRnIndex = -1;
        int index = 0;
        String[] header = new String[columnCount];
        for (int i = 0; i < columnCount; i++) {
            String s = metaData.getColumnName(i + 1);
            if ("RN".equalsIgnoreCase(s)) {
                skipRnIndex = i;
            } else {
                header[index++] = s;
            }
        }

        logger.info("header = ({})", String.join(",", header));

        List<Object[]> data = new ArrayList<>();
        while (resultSet.next()) {
            Object[] objects = new Object[columnCount];
            int cIndex = 0;
            for (int i = 0; i < columnCount; i++) {
                if (i == skipRnIndex) {
                    continue;
                }
                objects[cIndex++] = resultSet.getObject(i + 1);
            }
            data.add(objects);
        }
        return data;
    }

    public <T> List<T> autoMapper(ResultSet resultSet, Class<T> clazz) throws SQLException {
        List<T> list = new ArrayList<>();
        while (resultSet.next()) {
            final T t = AutoMapper.autoMapper(resultSet, clazz);
            if (t != null) {
                list.add(t);
            }
        }
        return list;
    }
}